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Abstract Detail


Holmes, Marion [1].

Symbiont limitation and environmental gradients shape dynamics of non-photosynthetic plants in post-agricultural forests.

Land-use legacies in plant communities have been attributed to factors including dispersal limitation and environmental legacies of past disturbance: species must be able to arrive in a successional site, and then establish once present. Less is known about the role of plant symbionts in shaping community assembly. Non-photosynthetic plants, obligate parasites, are a useful model system to understand the relative importance of symbiont presence, site history, and environmental gradients to succession in second-growth forests that have regrown after abandonment from agriculture. Disturbances such as agriculture disrupt populations of host plants by removing canopy trees or potentially damaging soil microbial communities. I tested the hypothesis that land-use history shapes parasitic plant distributions by altering host availability. Alternatively, environmental variation may be a more important predictor of species distributions.
Field sampling took place in Athens County, Ohio, in the Unglaciated Allegheny Plateau. Five parasitic plant species were selected, including two tree parasites and three mycoheterotrophs. I sampled populations in a replicated chronosequence of post-agricultural forest stands that consisted of five upland sites and five valley sites in each of four age classes: 40-60, 61-80, 81-100, and >130 years since canopy closure. All parasitic plants present were recorded, along with the number and basal area of host trees and all Fagaceae family species as a proxy for presence of the ectomycorrhizal fungi species parasitized by mycoheterotrophs. Host limitation showed a strong influence on distributions of parasitic plants. Tree parasites Conopholis americana and Epifagus virginiana had significant associations with host tree size. Mycoheterotroph abundance was similarly linked to basal area of Fagaceae family members, though the influence of other factors varied between species. Hypopitys monotropa was limited to forests >100 years old on South and West-facing aspects, Monotropa uniflora was associated with upland older forests, supporting the hypothesis of environmental filtering as an influence on distributions. Corallorhiza odontorhiza was unique in being most abundant in forests >80 years old, suggesting a disturbance-oriented life history, as well as an affinity for high-elevation upland sites. The relationships of parasitic plants with land-use history are therefore complex and species specific and represent the interactions of land-use history with host availability and edaphic gradients. These results support the hypothesis of symbiont-limitation as an assembly process influencing post-agricultural community dynamics.

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1 - University of Pittsburgh, Biological Sciences, Pittsburgh, PA, USA

land-use history
parasitic plants
plant community ecology.

Presentation Type: Oral Paper
Session: ECO8, Ecology: Interactions
Location: /
Date: Friday, July 23rd, 2021
Time: 10:15 AM(EDT)
Number: ECO8002
Abstract ID:523
Candidate for Awards:None

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